TRANSACTIONS OF THE SECTIONS. 101 
nerves becoming so close that it may be difficult, perhaps impossible, to define their 
respective limits. -Pfliiger has figured the nuclei of the cells of the alveoli of the 
salivary glands, the salivary cells, connected with a delicate fibre, which often 
pierces the surface of the cell in contact with the membrana propria, and gives 
the cell the appearance of being stalked. This appearance has also been seen by 
Schliiter, Otto Weber, Gianuzzi, Boll, and Kolliker; and, indeed, the appearance 
which Pfliiger has figured may be seen by any one who will take the trouble to 
examine the salivary glands of the common cockroach (Blatta orientalis). This 
rocess was shown to me by my friend and’ pupil, Mr. Charles Workman; and I 
ve several preparations which show a similar process to that which Pfliger has 
observed and figured ; but that it is as clearly connected with the nucleus of the cell 
as he describes it I am not prepared to affirm. Pfliiger says it is hollow, and often 
ee a large quantity of tenacious material which clearly proceeds from the 
nucleus. 
In the interior of the gland there are ducts lined with a thick but single layer of 
columnar epithelium, the cells of which are clear and uucleated near their free end, 
but furnished with a large number of extremely fine varicose hairs at the end con- 
nected with the membrana propria. This epithelium becomes thicker as the ducts 
proceed towards their connexion with the alveoli; and as transparent drops can be 
seen transuding from the ends of the cells when saliva has been made to flow by 
invitation of the gland, Pfltiger concludes that they are important secretory organs. 
Such ducts frequently form loops, or bend suddenly, or possess diverticula. The 
epithelium of the ducts, which carry the secretion out of the gland, is of a different 
and apparently less important lind. 
Pfluger directs special attention to the great number of nerves connected with the 
alveoli. He has identified them in fresh specimens by their investment here and 
there by an ordinary double-contoured medulla, by their being blackened by perosmic 
acid, by their varicosities, and by tracing them to larger and more easily recogni- 
zable nerves. He finds them branching in great numbers amongst the cells of the 
alyeoli, and traces their fibrils to the nuclei of the cells, sometimes after they have 
been connected with multipolar ganglion-cells. Or nerves covered by medulla and 
sheath, and containing numerous varicose axis cylinders, branch, enlarge, and 
become covered with protoplasm set with nuclei, forming what Pfltiger calls a 
protoplasmic foot, and supposes to be a structure intermediate in character between 
neryous and glandular tissue. And on the surface of the ducts lined by columnar 
epithelium a nerve divides into a pencil-like tuft of varicose fibrils, each of which 
Pfliiger says is directly continuous with one of the processes of a columnar epithelial 
cell. I have frequently seen the pencil-like tuft of varicose fibrils on the surface of 
the ducts lined by columnar epithelium; but it is not so easy to be sure that the 
fibrils are connected with the processes of the cells. However, the statement is 
made in the most positive way by Pfliiger, who has made these glands the subjects 
of very special and lengthened investigation; and his drawings afford very strong 
- corroborative testimony of the value of his statements. Moreover, in independent 
observations on the pancreas, he has also traced the nerves to endings in the secre- 
ting cells. 
But Pfliiger has gone greatly further than this. He has figured the hair-like 
processes at the attached end of the columnar cells in all stages of transition into 
salivary cells of new alveoli; and having previously found the nerves connected by 
varicose fibrils with protoplasmic masses set with nuclei, he concludes that it is 
ossible that the salivary cells are developed on the ends of the nerves without 
interference of their own nuclei, and that, as a continual new formation of alveoli 
and salivary cells implies the atrophy and disintegration of corresponding older 
parts, the alveoli with pale offshoots of various forms which he has seen in moles 
are evidences of such atrophy. : 
With these numerous instances in which nerves are alleged to pass through 
membranes to be connected with the cells on their surfaces, as if these were their 
special modes of termination, we might well be content until there has been time 
for further investigation by independent observers. But there are yet other in- 
stances. Langerhans described, in 1868, a fine network of fibres in the skin, from 
the superficial part of which fine non-medullated fibres pass out of the cutis and 
